The present invention relates to a keyboard structure of an electronic musical instrument.
In an electronic musical instrument having a keyboard, it is essential to cause a key touch to have a desired characteristic which is preferable for players. Various structures have been proposed to obtain the desired characteristic and various improvements thereof have been made.
In a typical prior art construction, a key return spring member is provided at the rearward end of each key and an L-shaped stopping member is provided near the forward end of the key to engage a keyboard frame disposed beneath the key for limiting the upward rotation of the key. With such construction, a troublesome operation is required for adjusting the key touch. More particularly, the key touch adjusting operation includes the alignment of the height of a plurality of juxtaposed keys, and the adjustments of depression key touches and release key touches of respective keys to have uniform characteristics. In the prior art construction, however, the position of the returning spring member and the position at which the upper limit stopping member engages the frame are spaced considerably in the longitudinal direction of each key, so that after one of the members of one key is adjusted, it is necessary to depress the key to check the key touch and then adjust the remaining member or to adjust the one member once more.
Due to the large space described above between the return spring member and the upper limit stopping members, an adjuster must extend his hand different distances for adjusting respective members, which results in a different feeling of adjustment as well as a long time for effecting this fine and delicate key touch adjustment. Furthermore, in the key construction described above, the returning spring member applies a downward force at the rearward end of each key, while the upper limit stopping member applies an upward force to the frame at the forward end of the key. As a consequence, the strain acting in the vertical direction of the frame increases toward its center. In other words, the strain of the frame is greatest at its longitudinal center of the key array, thus bending or distorting the keyboard.